Table 4. Association Between Severity of 12-Month
World Mental Health−Composite International Diagnostic Interview/Diagnostic and Statistical Manual of Mental Disorders, Fourth
Edition Disorders and Days Out of Role

Hagnell O. A Prospective Study of the Incidence of Mental Disorder:
A Study Based on 24,000 Person Years of the Incidence of Mental Disorders
in a Swedish Population Together With an Evaluation of the Aetiological Significance
of Medical, Social, and Personality Factors. Lund, Sweden: Svenska Bokforlaget; 1966.

Murray CJL, Lopez AD. The Global Burden of Disease: A Comprehensive Assessment
of Mortality and Disability From Diseases, Injuries and Risk Factors in 1990
and Projected to 2020. Cambridge, Mass: Harvard University Press; 1996.

Andrade L, de Lolio C, Gentil V, Laurenti R, Werebe D. Lifetime prevalence of mental disorders in a catchment area in Sao
Paulo, Brazil. In: Program and abstracts of the 7th Congress of the International
Federation of Psychiatric Epidemiology; August 1996; Santiago, Chile.

Robins LN, Wing J, Wittchen H-U.
et al. The Composite International Diagnostic Interview: an epidemiologic
instrument suitable for use in conjunction with different diagnostic systems
and in different cultures. Arch Gen Psychiatry.1988;45:1069-1077.PubMedGoogle Scholar

Allgulander C. Psychoactive drug use in a general population sample, Sweden: correlates
with perceived health, psychiatric diagnoses, and mortality in an automated
record-linkage study. Am J Public Health.1989;79:1006-1010.PubMedGoogle Scholar

Design, Setting, and Participants Face-to-face household surveys of 60 463 community adults conducted
from 2001-2003 in 14 countries in the Americas, Europe, the Middle East, Africa,
and Asia.

Main Outcome Measures The DSM-IV disorders, severity, and treatment
were assessed with the WMH version of the WHO Composite International Diagnostic
Interview (WMH-CIDI), a fully structured, lay-administered psychiatric diagnostic
interview.

Results The prevalence of having any WMH-CIDI/DSM-IV disorder
in the prior year varied widely, from 4.3% in Shanghai to 26.4% in the United
States, with an interquartile range (IQR) of 9.1%-16.9%. Between 33.1% (Colombia)
and 80.9% (Nigeria) of 12-month cases were mild (IQR, 40.2%-53.3%). Serious
disorders were associated with substantial role disability. Although disorder
severity was correlated with probability of treatment in almost all countries,
35.5% to 50.3% of serious cases in developed countries and 76.3% to 85.4%
in less-developed countries received no treatment in the 12 months before
the interview. Due to the high prevalence of mild and subthreshold cases,
the number of those who received treatment far exceeds the number of untreated
serious cases in every country.

Conclusions Reallocation of treatment resources could substantially decrease the
problem of unmet need for treatment of mental disorders among serious cases.
Structural barriers exist to this reallocation. Careful consideration needs
to be given to the value of treating some mild cases, especially those at
risk for progressing to more serious disorders.

Although surveys of mental disorders have been carried out since the
end of World War II,1- 3 cross-national
comparisons were hampered by inconsistencies in diagnostic methods. This situation
changed in the 1980s with the development of the Diagnostic Interview Schedule
(DIS), the first psychiatric diagnostic interview designed for use by lay
interviewers.4 The DIS was initially used in
the US Epidemiologic Catchment Area (ECA) Study and subsequently in similar
surveys carried out in other countries in the 1980s.5- 8 The
results were brought together in the early 1990s in a series of important
cross-national articles that showed mental disorders to be highly prevalent.9- 12 Indeed,
prevalence of mental disorder was generally higher than that of any other
class of chronic conditions.13,14 This
was striking in light of research documenting that mental disorders have greater
effects on role functioning than many serious chronic physical illnesses.13,15,16 A second generation
of cross-national psychiatric surveys was carried out in the 1990s17- 24 using
a more elaborate interview, the World Health Organization (WHO) Composite
International Diagnostic Interview (CIDI).25 Although
prevalence varied widely, more than one third of respondents typically met
criteria for a lifetime CIDI disorder.26 Survey-specific
treatment questions showed uniformly that most mental disorders were untreated.27,28

Before concluding that unmet need for treatment of mental disorders
is a major problem, it is important to recognize that many mental disorders
are mild and self-limiting. This was not a focus of the DIS or CIDI surveys,
which were designed to estimate prevalence rather than severity. However,
the high prevalence estimates in these surveys raised concerns that even the
richest of countries could not afford to treat all the people with a mental
disorder.29,30 Motivated by this
concern, investigators performed secondary analyses of 2 US surveys,8,20 which concluded that up to half of
12-month mental disorders were mild.31 Another
secondary analysis of CIDI surveys in 5 developed countries found a similar
proportion of mild cases28 and showed that
treatment was consistently correlated with severity. Between one third and
two thirds of serious cases in these surveys nevertheless received no treatment.

The DIS and CIDI surveys had 3 limitations to analysis of severity and
treatment. First, as they were designed to assess prevalence, not severity,
the post hoc measures of severity used in secondary analyses of these surveys
were weak. Second, the interviews did not include standardized treatment questions,
thwarting valid cross-national comparisons of treatment. Third, the surveys
were carried out mostly in developed countries, making it impossible to assess
generalizability of results. WHO established the World Mental Health (WMH)
Survey Consortium in 1998 to address such limitations.32 The
CIDI was expanded to include detailed questions about disorder severity, impairment,
and treatment.33 Coordinated WMH-CIDI surveys
were then implemented in 28 countries around the world, including less-developed
countries in each region of the world. The WMH surveys have now been completed
in 14 countries, 6 of them less developed. This article is the first joint
publication from these surveys. The focus is on aggregate estimates of 12-month
prevalence, severity, and treatment.

Methods

Samples

Fifteen surveys were carried out in 14 countries in the Americas (Colombia,
Mexico, United States), Europe (Belgium, France, Germany, Italy, Netherlands,
Spain, Ukraine), the Middle East and Africa (Lebanon, Nigeria), and Asia (Japan,
separate surveys in Beijing and Shanghai in the People's Republic of China).
Six countries are classified by the World Bank34 as
less developed (China, Colombia, Lebanon, Mexico, Nigeria, and Ukraine) and
the others as developed. An effort was made to recruit as many countries as
possible in the intiative. The final set was determined by availability of
collaborators in the country who were able to obtain funding for the survey.
All surveys were based on multistage household probability samples (Table 1). All interviews were carried out
face-to-face by trained lay interviewers. The 6 Western European surveys were
carried out jointly.35 Sample sizes range from
1663 (Japan) to 9282 (United States), with a total of 60 463 participating
adults. Response rates range from 45.9% (France) to 87.7% (Colombia), with
a weighted average of 69.9%.

Internal subsampling was used to reduce respondent burden by dividing
the interview into 2 parts. Part 1 included core diagnostic assessment. Part
2 included information about correlates and disorders of secondary interest.
All respondents completed part 1. All part-1 respondents who met criteria
for any disorder and a subsample of approximately 25% of others were administered
part 2. The part-2 sample included 25 828 respondents. Noncertainty part-2
respondents were weighted by the inverse of their probability of selection
to adjust for differential sampling. Analyses in this article are based on
this weighted part-2 sample. Additional weights were used to adjust for differential
probabilities of selection within households and to match the samples to population
sociodemographic distributions. The samples show substantial cross-national
differences in age structure (younger in less-developed countries) and educational
status (lower in less-developed countries). (Demographic distributions available
on request.)

Training and Field Procedures

The central WMH staff trained bilingual supervisors in each country.
Consistent interviewer training documents and procedures were used across
surveys. The WHO translation protocol was used to translate instruments and
training materials. Two surveys were carried out in bilingual form (Dutch
and French in Belgium; Russian and Ukrainian in Ukraine). Others were carried
out exclusively in the country's official language (or, in Nigeria, in the
Yoruba language that dominates in the region where the survey was carried
out). Persons who could not speak these languages were excluded. Standardized
descriptions of the goals and procedures of the study, data uses and protection,
and the rights of respondents were provided in both written and verbal form
to all predesignated respondents before obtaining verbal informed consent
for participation in the survey. Quality control protocols described in more
detail elsewhere36 were standardized across
countries to check on interviewer accuracy and to specify data cleaning and
coding procedures. The institutional review board of the organization that
coordinated the survey in each country approved and monitored compliance with
procedures for obtaining informed consent and protecting human subjects.

Measures

All surveys used the WMH-CIDI, a fully structured diagnostic interview,
to assess disorders and treatment. Disorders considered herein include anxiety
disorders (agoraphobia, generalized anxiety disorder, obsessive-compulsive
disorder, panic disorder, posttraumatic stress disorder, social phobia, specific
phobia), mood disorders (bipolar I and II disorders, dysthymia, major depressive
disorder), disorders that share a feature of problems with impulse control
(bulimia, intermittent explosive disorder, and adult persistence of 3 childhood-adolescent
disorders—attention-deficit/hyperactivity disorder, conduct disorder,
and oppositional-defiant disorder—among respondents in the 18- to 44-year
age range), and substance disorders (alcohol and drug abuse and dependence).
Disorders were assessed using the definitions and criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).37 CIDI organic
exclusion rules were imposed in making all diagnoses. Methodological evidence
collected in the WHO-CIDI Field Trials and later clinical calibration studies
showed that all the disorders considered herein were assessed with acceptable
reliability and validity both in the original CIDI38 and
in the original version of the WMH-CIDI.39 Studies
of cross-national comparability in the validity of the WMH-CIDI are currently
underway.

WMH-CIDI/DSM-IV disorders were classified as
serious, moderate, or mild. Serious disorders were defined as one of the following:
meeting criteria for bipolar I disorder or substance dependence with a physiological
dependence syndrome; making a suicide attempt in conjunction with any other
WMH-CIDI/DSM-IV disorder; reporting at least 2 areas
of role functioning with severe role impairment due to a mental disorder in
the disorder-specific Sheehan Disability Scales40;
or reporting overall functional impairment at a level consistent with a Global
Assessment of Functioning41 of 50 or less in
conjunction with any other WMH-CIDI/DSM-IV disorder.
Respondents not classified as having a serious disorder were classified as
moderate if interference was rated as at least moderate in any Sheehan Disability
Scales domain or if the respondent had substance dependence without a physiological
dependence syndrome. All other disorders were classified as mild. In an effort
to validate severity ratings, respondents were asked how many days out of
365 in the past 12 months they were totally unable to carry out their normal
daily activities because of each disorder. These reports were combined by
assigning respondents who had more than 1 disorder to the highest number of
days out of role reported for any single disorder.

Twelve-month treatment was assessed by asking respondents if they ever
saw any of a long list of professionals either as an outpatient or inpatient
for problems with emotions, nerves, mental health, or use of alcohol or drugs.
Included were mental health professionals (eg, psychiatrist, psychologist),
general medical professionals (eg, general practitioner, occupational therapist),
religious counselors (eg, minister, sheikh), and traditional healers (eg,
herbalist, spiritualist). The list varied across countries depending on local
circumstances. We focus herein on 12-month treatment by either a mental health
professional or general medical professional.

Analysis Methods

Data are reported on prevalence, severity, and associations of severity
with days out of role and with treatment. Simple cross-tabulations were used
to calculate prevalence and severity. Associations of severity with days out
of role and treatment were examined using analysis of variance. Confidence
intervals were estimated using the Taylor Series method42 with
SUDAAN software43 to adjust for clustering
and weighting. Multivariate tests were made using Wald χ2 and
F tests computed from design-adjusted coefficient variance–covariance
matrices. Statistical significance was based on 2-sided tests evaluated at
the .05 level of significance.

Results

Prevalence

Overall prevalence varies widely (Table 2), from 4.3% in Shanghai to 26.4% in the United States, with
a 9.1% to 16.9% inter-quartile range (IQR, the range after excluding the highest
and lowest 4 surveys). Anxiety disorders are the most common disorders in
all but 1 country (higher prevalence of mood disorders in Ukraine), with prevalence
in the range 2.4% to 18.2% (IQR, 5.8%-8.8%). Mood disorders are next most
common in all but 2 countries (equal or higher prevalence of substance disorders
in Nigeria and Beijing), with prevalence in the range 0.8% to 9.6% (IQR, 3.6%-6.8%).
Substance disorders (12-month prevalence, 0.1%-6.4%; IQR, 0.8%-2.6%) and impulse-control
disorders (12-month prevalence, 0.0%-6.8%; IQR, 0.7%-1.7%) are consistently
less prevalent across the surveys. If we use the terms high and low to refer to the 5 highest and
5 lowest prevalence estimates in each column of the table, the United States
and Colombia have consistently high prevalence estimates across all classes
of disorder, the Netherlands and Ukraine are high on 3 of 4, Nigeria and Shanghai
are consistently low, and Italy is low on 3 of 4.

Severity

The proportions of the samples (Table
3) with either a serious disorder (0.4%-7.7%; IQR, 1.1%-3.7%) or
a moderate disorder (0.5%-9.4%; IQR, 2.9%-6.1%) are generally smaller than
the proportions with a mild disorder (1.8%-9.7%; IQR, 4.5%-6.4%). The proportion
of disorders classified as mild is substantial: from 33.1% in Colombia to
80.9% in Nigeria (IQR, 40.2%-53.3%). The severity distribution among cases
varies significantly across countries (χ228= 193.9, P <.001), with severity not strongly related either
to region or to development status. There are substantial positive associations,
however, between overall prevalence of any disorder and both the proportion
of cases classified as serious (Pearson r = 0.56; P = .03) and the proportion of cases classified as either
serious or moderate (Pearson r = 0.51; P = .05).

Severity and Impairment

The severity classification was validated by documenting a statistically
significant monotonic association between severity and days out of role in
all but 2 surveys (Table 4). Respondents
with serious disorders in most surveys reported at least 30 days in the past
year when they were totally unable to carry out usual activities because of
these disorders (IQR, 32.1-81.4 days). The mean days out of role for mild
disorders, in comparison, is low in all surveys (0.1-3.6 days) while the mean
for moderate disorders is intermediate between these extremes (4.1-33.7 days;
IQR, 9.2-18.8 days). Even the means for moderate disorders are larger than
those found in previous research to be associated with most serious chronic
physical disorders.13,44

Severity and Treatment

The proportion of respondents who received health care treatment for
emotional or substance-use problems during the 12 months before the WMH interview
varies widely across surveys (Table 5),
from a low of 0.8% in Nigeria to a high of 15.3% in the United States. Predictably,
the proportion in treatment is much larger in developed than in less-developed
countries. However, despite this wide variation, a meaningful association
exists between disorder severity and probability of treatment in every survey.
The proportion in treatment is much higher among serious cases (49.7%-64.5%
in developed vs 14.6%-23.7% in less developed countries) than moderate cases
(16.7%-50.0% in developed vs 9.7%-18.6% in less developed countries), and
lower still among mild cases (11.2%-35.2% in developed vs 0.5%-10.2% in less
developed countries). A small proportion of noncases also received treatment
(2.4%-8.1% in developed countries and 0.3%-3.0% in less developed countries),
presumably reflecting the joint effects of the WMH-CIDI not assessing all
mental disorders, some true cases of the disorders being incorrectly classified
as noncases, and some people in treatment not meeting criteria for a DSM-IV disorder.

Even though the proportion of noncases in treatment is small, the fact
that noncases make up the vast majority of the population means that noncases
constitute a meaningful fraction of all people in treatment. In fact, calculations
based on Table 3 and Table 5 show that either the majority or
a near majority of people in treatment in each country are either noncases
or mild cases. (Results available on request.) These will be referred to for
the remainder of this article as subthreshold cases. We also examined the
associations of severity with 2 indicators of treatment intensity among people
in health care treatment: being seen in the specialty mental health sector
rather than exclusively in the general medical sector and number of visits
in the 12 months before the interview. Statistical power was low in these
analyses because of the small numbers of treated cases with serious conditions
in most countries. Nevertheless, there was a clear trend in the vast majority
of countries for severity to be positively related both to proportional treatment
in the specialty sector and to number of visits, with the highest scores on
each consistently found among serious cases. (Results available on request.)

Even though a dose-response relationship exists between severity and
probability of treatment in virtually all countries, substantial proportions
of serious cases receive no treatment. This is true even in developed countries,
where 35.5% to 50.3% of serious cases were untreated in the health care sector
in the year before the interview. The situation is even worse in less-developed
countries, where 76.3% to 85.4% of serious cases received no treatment. This
is especially striking in light of the fact that such a high proportion of
treatment in all countries is devoted to subthreshold cases. It is interesting
to note that the 3 surveys with the highest overall 12-month prevalence estimates
(United States, Ukraine, and Colombia) also had 3 of the 4 lowest proportions
of treatment devoted to subthreshold cases (52%-59%). In comparison, the 3
Asian surveys, all of which had quite low overall 12-month prevalence estimates,
had the 3 highest proportions of treatment devoted to subthreshold cases (71%-85%).

Comment

An important limitation of the WMH surveys is their wide variation in
response rate. In addition, some of the surveys had response rates below normally
accepted standards. We attempted to adjust for differential response to the
extent possible by poststratification, but this only deals with a limited
type of bias. If response is related to mental illness, severity, or treatment
in ways that cannot be corrected by simple sociodemographic adjustment, cross-national
comparisons will be distorted.

A related limitation is that the Western European surveys, which were
fielded before any of the other WMH surveys, experienced a number of difficulties
in survey implementation, largely skip logic errors, that subsequent surveys
avoided because they were resolved while carrying out the Western European
surveys. As a result, these early surveys had much more item-missing data
than later surveys, which led to underestimation of severity of some disorders
because the Sheehan Disability Scales were sometimes mistakenly skipped.

An added complication was that various of the WMH surveys deleted disorders
that were thought to have low relevance in their countries, leading to inconsistency
in completeness of coverage. We investigated the implications of this variation
by replicating analyses using only the disorders that were assessed in all
surveys. Although basic patterns of association remained stable in these revised
analyses (results available on request), it is still possible that some findings
were sensitive to differential exclusion of some disorders in particular countries.

Another limitation is that schizophrenia and other nonaffective psychoses,
although important mental disorders, were not included in the core WMH assessment
because previous validation studies showed they are dramatically overestimated
in lay-administered interviews like the WMH-CIDI.44- 49 These
same studies also showed, however, that the vast majority of respondents with
clinician-diagnosed nonaffective psychoses meet criteria for CIDI anxiety,
mood, or substance disorders and are consequently captured as cases even if
nonaffective psychoses are not assessed.

A final noteworthy limitation is that the WMH-CIDI might vary in accuracy
across countries. Although the previous methodological studies that were cited
in the measurement section documented that earlier versions of the CIDI had
acceptable concordance with blind clinical reinterviews, these studies were
carried out largely in developed Western countries. Performance of the WMH-CIDI
could be worse in other parts of the world either because the concepts and
phrases used to describe mental syndromes are less consonant with cultural
concepts than in developed Western countries or because absence of a tradition
of free speech and anonymous public opinion surveying causes greater reluctance
to admit emotional or substance-abuse problems than in developed Western countries.

Clinical reappraisal studies are currently underway in both developed
and less developed WMH countries in all major regions of the world to evaluate
the issue of cross-national differences in WMH-CIDI diagnostic validity. Even
before completing these studies, though, some patterns in the data (eg, the
much lower estimated rate of alcoholism in Ukraine than expected from administrative
data documenting an important role of alcoholism in mortality in that country50) raise concerns about differential validity. The
most striking such pattern is that countries with the lowest disorder prevalence
estimates have the highest proportion of respondents in treatment who are
subthreshold cases. This pattern could very well reflect greater underestimation
of disorders in countries with the lowest prevalence estimates.

Within the context of these limitations, the WMH results are consistent
with those of earlier surveys in showing that mental disorders are highly
prevalent,9- 12 often
are associated with serious role impairment,15,16,51 and
often go untreated.27,28,52 We
also found substantial cross-national variation in these results. Two broad
patterns consistent with previous research are that prevalence is low in Asian
countries9- 12,53 and
that treatment is low in less developed countries.26 There
are so many idiosyncratic substantive and methodological factors that might
contribute to these and other cross-national differences that it is more profitable
to focus on consistency rather than on differences, at least in this initial
report of broad WMH findings. It is noteworthy in this regard that prevalence
and severity estimates are likely to be conservative, for previous methodological
studies have shown that survey nonrespondents tend to have significantly higher
rates and severity of mental illness than respondents.20,36,54,55 The
estimates of proportional treatment, in comparison, are likely to be downwardly
biased because hospitalized patients were excluded from the surveys.

We found that disorder severity is strongly related to treatment in
all countries. This finding is consistent with 2 previous large-scale survey
investigations of the relationship between severity and treatment.28,52 Correction for response bias would
likely strengthen this relationship. The most reasonable interpretation is
that demand for treatment is related to severity, presumably mediated by distress
and impairment. A question could be raised whether this is merely a matter
of demand or whether the treatment system is also more receptive to more severe
cases. Some indirect indication of system responsiveness can be gleaned from
the findings (available on request) that treatment intensity, as indicated
by proportional treatment in the specialty sector and number of visits, is
greater for serious than for other treated cases in most WMH countries.

Despite this evidence of rationality in treatment resource allocation,
we found that 35.5% to 50.3% of serious cases in developed countries and 76.3%
to 85.4% in less developed countries received no treatment in the 12 months
before the survey. Yet a majority of people in treatment in most of the countries
were subthreshold cases. Correction for response bias would likely show that
we underestimated the proportion of serious cases in treatment more than the
proportion of subthreshold cases in treatment, leading to this pattern becoming
even stronger. The fact that many people with subthreshold disorders are treated
while many with serious disorders are not shows that unmet need for treatment
among serious cases is not merely a matter of limited treatment resources
but that misallocation of treatment resources is also involved.

A major practical difficulty in rationalizing allocation of treatment
resources is that system barriers constrain reallocation options. This is
especially true in a decentralized system like in the United States. For example,
there is no obvious mechanism by which constraining access to psychotherapy
among middle-class persons with mild mental disorders in the United States
would result in an increase in treatment of low-income people with serious
mental illness. Another complexity is that misallocation of treatment resources
is partly due to differences in perceived need for treatment that are unrelated
to objective severity and to differences in access associated with insurance
coverage and financial resources.28,52,56 A
report comparing the mental health care delivery systems in the United States
and Ontario showed that these 2 systems differ along exactly these lines.56 A higher proportion of people with serious mental
illness were treated in Ontario than were treated in the United States because
of lower constraint on access among persons unable to pay in Ontario than
were able to pay in the United States while a higher proportion of mild cases
were treated in the United States than Ontario because of significantly higher
perceived need for treatment among insured middle-class people with mild disorders
in the United States than in Ontario. Although a number of structural possibilities
exist to modify constraints on access, it is unclear how perceived need could
be modified to align demand with true need for treatment.

A final complexity in reallocating treatment resources is that optimal
allocation rules are not obvious. The simplistic strategy of not treating
any mild disorders is almost certainly suboptimal31 because
we know that many people with mild disorders, especially young people, go
on to develop serious mental disorders.57 To
the extent that early intervention can prevent progression, early treatment
of mild cases might be cost effective.58 It
is difficult to act on this insight, however, because we lack good information
either about the characteristics of mild cases that predict risk of progression
to more serious disorders or about the effectiveness of interventions for
mild cases in preventing this progression. A new focus on the development
and evaluation of secondary prevention programs for the early treatment of
mild cases is needed to guide rationalization of treatment resource allocation.

Hagnell O. A Prospective Study of the Incidence of Mental Disorder:
A Study Based on 24,000 Person Years of the Incidence of Mental Disorders
in a Swedish Population Together With an Evaluation of the Aetiological Significance
of Medical, Social, and Personality Factors. Lund, Sweden: Svenska Bokforlaget; 1966.

Murray CJL, Lopez AD. The Global Burden of Disease: A Comprehensive Assessment
of Mortality and Disability From Diseases, Injuries and Risk Factors in 1990
and Projected to 2020. Cambridge, Mass: Harvard University Press; 1996.

Andrade L, de Lolio C, Gentil V, Laurenti R, Werebe D. Lifetime prevalence of mental disorders in a catchment area in Sao
Paulo, Brazil. In: Program and abstracts of the 7th Congress of the International
Federation of Psychiatric Epidemiology; August 1996; Santiago, Chile.

Robins LN, Wing J, Wittchen H-U.
et al. The Composite International Diagnostic Interview: an epidemiologic
instrument suitable for use in conjunction with different diagnostic systems
and in different cultures. Arch Gen Psychiatry.1988;45:1069-1077.PubMedGoogle Scholar

Allgulander C. Psychoactive drug use in a general population sample, Sweden: correlates
with perceived health, psychiatric diagnoses, and mortality in an automated
record-linkage study. Am J Public Health.1989;79:1006-1010.PubMedGoogle Scholar